Bifocal contact lens and method of making same

ABSTRACT

A bifocal contact lens is provided having a posterior surface that is formed to fit a human cornea and an anterior surface. The bifocal contact lens has an upper portion and a lower portion when viewed in a planar view. The anterior surface includes a distance vision surface and a near vision surface. The distance vision surface is substantially semicircular in form and located in the upper portion of the bifocal lens. A near vision surface is disposed within the lower portion of the bifocal contact lens and also surrounds the distance vision surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an improved bifocal contactlens and in particular to an improved single axis alternating visionbifocal contact lens. Still more particularly, the present inventionprovides an improved single axis alternating vision bifocal contact lensthrough a combination of distance vision and near vision sections.

2. Description of the Related Art

Contact lenses are now widely used for the correction of many differenttypes of vision deficiencies. One deficiency is a condition occurs as aperson ages--the lens of the eye begins to crystalize and lose itselasticity, eventually resulting in the eye losing the ability to focuson objects which are nearby. This condition is called presbyopia. Acorrective lens to accommodate for the eye's weakness and properly focuslight on the retina is needed in this condition.

One way to correct this problem is for a presbyopic person to wearreading glasses when it is desirable to see things nearby. Some peoplerequire both correction for near and far vision. In this situation,bifocal eye glasses have been prescribed for many years. These eyeglasses correct for distance vision through one section of the lens andcorrect for near vision through a second section of the lens. Manypeople do not like to wear bifocal eye glasses and would prefer to wearcontact lenses to correct their vision.

Bifocal contact lenses have been designed and manufactured in theindustry for many years. Some designs involve a principle ofsimultaneous vision. For example, U.S. Pat. No. 4,923,926 teaches theutilization of a pair of corrective lenses whose surfaces are dividedinto a series of discrete near and distance vision zones whosedimensions and positions are such that, relative to the line of sight ofthe right and left eye respectively, each zone on one lens containingthe distance power corresponds to a similar zone on the other lenscontaining a near power correction. These simultaneous vision oraspheric bifocal contact lenses have experienced some success, but areusually limited to early presbyopic or low add powers. Problems stillexist, however, in providing presbyopic patients with a bifocal contactlens which successfully provides correction for both near and distancevision.

U.S. Pat. No. 4,869,587 discloses a multifocal contact lens of theconcentric simultaneous vision type. That is, the lens includes a prismballast at a lower edge such that the center of the near portion of lensis offset below the center of the wearer's pupil, leaving acrescent-shaped portion of the pupil covered by the distance portionrather than the near portion of the contact lens. A prism or prism shapeis produced during manufacturing of a lens by making the lens thicker,and thus, heavier, at the lower portion of the lens. Thus, ballast orprism ballast is accomplished. This type of lens involves some blurringof images since light always passes through a portion of the lens thatis out of focus.

Another type of bifocal contact lens is based on the alternating visionprinciple. "Alternating vision" is a term utilized to describe a bifocalcontact lens which contains a distance vision section in the upperportion of the lens and a near vision section in the lower portion ofthe lens. One type of alternating vision lens is an annular typedisclosed in U.S. Pat. No. 4,971,432, involving a distance visionsection concentric with a near vision section. Another is a crescentsegmented bifocal contact lens such as that disclosed in U.S. Pat. No.4,928,583 as having a distance portion above and a crescent shapedportion immediately below the distance portion.

U.S. Pat. No. 4,693,572 teaches a bifocal contact lens divided into adistance vision segment in the upper part of the lens and a near visionsegment in the lower portion of the lens. This lens is manufactured byremoving weight from the bottom portion of the lens and, thus, requiresthe lens to be much thicker when prism is desired.

Although many bifocal contact lens designs exist, the monovision systemof contact lenses presently remains the most prescribed form of fittingpresbyopic patients in contact lenses. This monovision system requiresfitting a distance power lens in one eye and a near vision power lens inthe other eye. Moreover, monovision also compromises a patient's abilityto retain depth perception and has a low success rate. The prevalence ofthe monovision system is an indication that many improvements are stillneeded in the bifocal contact lens field.

Additionally, with the increasing use of computers, more and more peopleutilize a computer at work and at home. An ability to have near visionwhen glancing up at a video display screen is helpful in addition to thenear vision utilized while looking downward. Moreover, situations existin which near vision is desired when looking side to side. For example,a car driver may wish to glance to one side to find controls or readinstruments in a car. Presently, alternating vision bifocal contactlenses provide distance vision when looking up or straight ahead andnear vision when looking downward, but near vision is not supported forglancing up from a desk or side to side to read controls or instruments.

Further, many translating bifocal contact lenses require large amountsof prism, or added weight to keep the lens oriented on the eye so thatthe near vision segment or section of the lens positions on the lowerhalf of the eye. Added prism ballast results in a lens that is thickerand thus more uncomfortable on a wearer's eye than lenses either notcontaining prism or containing lesser amounts of prism.

Consequently, it would be desirable to have a bifocal contact lens thatprovides near vision when glancing upward and side to side in additionto the normal downward reading and provides greater comfort to thewearer than previously known bifocal contact lenses.

SUMMARY OF THE INVENTION

It is therefore one object of the present invention to provide animproved bifocal contact lens.

It is yet another object of the present invention to provide an improvedsingle axis alternating vision bifocal contact lens.

It is still another object of the present invention to provide animproved single axis alternating vision bifocal contact lens through acombination of distance vision and near vision sections.

It is a further object of the present invention to provide an improvedsingle axis alternating vision bifocal contact lens which provides morecomfort for the wearer.

The foregoing objects are achieved as is now described. In accordancewith the apparatus of the present invention, a bifocal contact lens isprovided having a posterior surface that is formed to fit a humancornea. The bifocal contact lens has an upper portion and a lowerportion when viewed in a planar view. The anterior surface of the lenshas distance and near vision surfaces. The distance vision surface issubstantially semicircular in form and disposed in the upper portion ofthe contact bifocal lens. A first near vision surface is disposed withinthe lower portion of the lens. A second near vision surface surroundsthe distance vision surface in the upper portion of the lens.

The present invention also includes a method for making a bifocalcontact lens from a lens blank. The lens blank includes an anteriorsurface and a posterior surface and a upper portion and a lower portionin a planar view. A near vision surface is formed or cut on the anteriorsurface with the near vision surface having a first radius of curvature.Next, a distance vision surface is formed on the anterior surface inapproximately the upper portion of the lens blank in a generallysemicircular shape wherein the distance vision surface is surrounded bythe near vision surface. The near distance surface has a second radiusof curvature wherein the second radius of curvature is smaller than thefirst radius of curvature.

The above as well as additional objects, features, and advantages of thepresent invention will become apparent in the following detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself however, as well as apreferred mode of use, further objects and advantages thereof, will bebest understood by reference to the following detail description of anillustrative embodiment when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 depicts an isometric view of a bifocal contact lens having alenticular section which is manufactured in accordance with a preferredembodiment of the present invention;

FIG. 2 is a front view of a bifocal contact lens which is manufacturedin accordance with a preferred embodiment of the present invention;

FIG. 3 depicts a vertical sectional view of the bifocal contact lensdepicted in FIG. 2, taken along line 3--3 of FIG. 2;

FIG. 4 is a vertical sectional view of the bifocal 25 contact lensdepicted in FIG. 2 taken along line 4--4 of FIG. 2;

FIG. 5 depicts a vertical sectional view of the bifocal contact lensdepicted in FIG. 2 taken along line 5--5 of FIG. 2;

FIG. 6 is a front view of a bifocal contact lens which is manufacturedin accordance with a preferred embodiment of the present invention;

FIG. 7 depicts a sectional view of a bifocal contact lens with apreferred embodiment of a lenticular section in accordance with apreferred embodiment of the present invention;

FIG. 8 is a side view of a contact lens holder and a contact lens blank;

FIG. 9 depicts a partial side view of a lathe illustrating the cuttingof a distance segment in accordance with a preferred embodiment of thepresent invention; and

FIG. 10 is a partial top view of a lathe illustrating the cutting of anear vision segment in accordance a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

With reference now to the Figures, and in particular with reference toFIG. 1, there is depicted an isometric view of a bifocal contact lenshaving a lenticular section in accordance with a preferred embodiment ofthe present invention. As may be seen, lens 100 includes an anteriorsurface 102 which contains a near vision surface 104, surrounding adistance vision surface 106

In particular, distance vision surface 106 is located in a upper portion108 of lens 100 and near vision surface 104 is located in a lowerportion 110 of lens 100 and extends around distance vision surface 106in upper portion 108 of lens 100. Anterior surface 102 also includes afront lenticular surface 112 Front lenticular surface 112 is part of alenticular section 114 of lens 100. Lens 100 also includes radial edge116 Lenticular section 114 is utilized under a preferred embodiment ofthe present invention to allow lens 100 to be thinner and reduce themass of lens 100 than otherwise would be possible without lenticularsection 114.

Lenticular section 114 is preferably formed by changing the front radiusof curvature of lens 100 in the outer portion of the lens or peripheralportion in order to maintain consistent edge thickness and/or reducethickness or mass of the lens. Lenticular section 114 of lens 100contains a base curve and a peripheral curve. Lenticulation allows lens100 in a preferred embodiment of the present invention, to be greatlyreduced in mass and contributes strongly to eye comfort in the wearer ofthe lens.

Near vision surface 104 and distance vision surface 106 meet at a line118, which divides lens 100 into upper portion 108 and a lower portion110. Also at line 118, a shelf surface 120 having opposing ends 121 isformed by the meeting of near vision surface 104 and distance visionsurface 106. Shelf surface 120 is formed between an upper edge 122 ofnear vision surface 104 and a lower edge 124 of distance vision surface106. That is, shelf surface 120 is formed by an offset between upperedge 122 of near vision surface 104 and lower edge 124 of distancevision surface 106 along line 118, the line along which these twosurfaces meet. Shelf surface 120 extends along line 118 and extendsperpendicularly to at least one of the two surfaces. In actual use,shelf surface 120 faces an upper lid of a wearer.

FIG. 2 is a front view of a bifocal contact lens 100 which ismanufactured in accordance with a preferred embodiment the presentinvention. To reduce the complexity of the description of this Figureand others, those portions of the embodiments of the present inventionwhich are substantially similar to the portions illustrated in FIG. 1will be referred to utilizing the same reference numerals. Lens 100includes line 118 which generally divides lens 100 into upper portion108 and lower portion 110. Lower portion 110 of lens 100 forms firstzone 126 which contains near vision surface 104. Upper portion 108contains both near vision surface 104 and distance vision surface 106. Asecond zone 128 is formed by distance vision surface 106 in upperportion 108 of lens 100 and a third zone 130, in the form of an annularsemicircular segment around second zone 128, meets first zone 126 alongline 118.

Referring again to FIG. 1, shelf surface 120 is greatest in width at ornear the geometric center of lens 100 and decreases in width as radialedge 116 of lens 100 is approached until shelf surface 120 becomenonexistent near ends 121 of shelf surface 120. FIGS. 3-5 illustrate thechange in the width of shelf surface 120 as ends 121 of shelf surfaceare approached, under a preferred embodiment of the present invention.

It should also be apparent from FIG. 1 and FIGS. 3-5 that proximate toopposing ends 121 of shelf surface 120, near vision surface 104 anddistance vision surface 106 meet at a tangent, without an offset betweenthe surfaces. Thus no shelf surface 120 is formed since these surfacesmeet or are tangent to each other at a single point, and are nearlytangent at closely adjacent points. This decreasing of shelf surfacewidth towards radial edge 116 has an advantage of improving eye comforton the wearer a lens under a preferred embodiment of the presentinvention.

A bifocal lens under a preferred embodiment of the present inventionshould have the upper and lower portions of the lens proportioned suchline 118 lies substantially at the lower portion of the wearer's pupilin actual use.

FIG. 3 depicts a vertical sectional view of the bifocal lens in FIG. 2taken along line 3--3 of FIG. 2 under a preferred embodiment of thepresent invention. Lens 100 in this vertical sectional view is depictedhaving an optical axis line 140 where all centers of curvatures C-1, C-2and C-3 lie along optical axis line 140.

Rear surface 142 is formed on a radius R=1 with rear surface 142 havinga center of curvature C-1. Near vision segment 144 contains near visionsurface 104, having a radius of curvature R-2 and a center of curvatureC-2. Distance vision segment 146 has distance vision surface 106 whichhas a radius of curvature R-3 and a center of curvature C-3. Althoughthis particular embodiment of the present invention is shown as being a"monocentric" lens, this particular feature is not essential to thepresent invention and is described only for purposes of illustration ofa preferred embodiment of the present invention.

A bifocal contact lens constructed in accordance with the presentinvention may be a "single axis" lens, which is a lens having both thedistance vision section and the near vision section made with the sameprism.

FIG. 6 is a front view of a bifocal contact lens which includes alenticular section 114 in accordance with a preferred embodiment of thepresent invention. FIG. 6 is a front view of the lens of FIG. 1 Asdepicted, distance vision surface 106 is substantially the shape of asemicircle which is located in upper portion 108 of lens 100,encompassed by near vision surface 104 and forming a shelf surface alongline 118 where near vision surface 104 and distance vision surface 106meet. Lenticular section 114 is located in upper portion 108 of lens 100along radial edge 116.

FIG. 7 depicts a vertical sectional view of the bifocal contact lens ofFIG. 6. Lenticular section 114 has a front lenticular surface 112 and arear lenticular surface 148.

The contact lens of the present invention is a translating or singleaxis alternating vision bifocal lens design. The bifocal lens in apreferred embodiment of the present invention includes a near visionlens with a distance segment cut on the upper portion of the lens,permitting distance viewing only when distance viewing is necessary;i.e., looking straight ahead. In addition, removing weight from the topportion of the bifocal lens also contributes to eye comfort, but moreimportantly makes the lens "bottom heavy" which aids greatly in lensorientation. A "bottom heavy" lens requires less prism ballast and/orweight for adequate lens orientation and even further contributes tolens comfort on the eye of the wearer.

Referring to FIG. 8, there is illustrated a side view of a lens blank150 shown mounted on a lens holder 152, prior to forming the anteriorsurface of a bifocal contact lens in accordance with a preferredembodiment of the present invention.

Referring to FIG. 9, there is depicted a partial side view of a doublecompound lathe illustrating the cutting of a distance vision segment inaccordance with a preferred embodiment of the preferred embodiment ofthe present invention. A back surface is first cut into a lens blank150. Next, lens blank 150 is mounted on lens holder 152 with a pitch oradhesive. Lathe 154 contains a rotating spindle 156 with collet 158 forholding lens holder 152 in place during the forming of the front lenssurfaces. Lens blank 150 is rotated about an axis line 160 and cuttingtool 162 is manipulated to form a near vision surface and an opticalaxis coincident with axis line 160, in a first series of passes.

With reference to FIG. 10 there is depicted is a partial top view of asingle compound lathe showing the cutting of a near vision segment inaccordance with a preferred embodiment of the present invention. Lensholder 152 is removed from collet 158 and placed into a rod 164a locatedon collet 158awith the center hole 166 of rod 164a lined up with thecutting tool 162a perpendicular to the axis 160a. The optical axis oflens blank 150 is perpendicular to axis line 160a. The radius ofcurvature is set by the distance between tip 168 of cutting tool 162aand the point at which axis 160a cross aligning axis 170. The radius ofcurvature can be adjusted by changing the distance of tip 168 of cuttingtool 162a in relation to the point defined by the intersection of axis160a and aligning axis 170. Lens holder 152 is moved such that lensblank 150 meets tip 168 in order to position lens blank 150 for a secondseries of passes to cut the radius for the distance vision section.Next, lens blank 150 is rotated such that the optical axis of lens 150is perpendicular to axis 160a and a second series of passes are madeutilizing cutting tool 162a to form a distance vision surface in asemicircular shape located centrally in an upper portion of the lens.

In accordance with a preferred embodiment of the present invention, abifocal lens may be produced as a rigid gas permeable lens, a softcontact lens, or some other form of plastic contact lens.

One advantage of a bifocal contact lens manufactured in accordance withthe present invention is that the decrease in the width of the shelfsurface as the radial edges of the lens are approached aids inincreasing comfort to the wearer of the lens. Furthermore, the locationof the distance vision segment of the lens in relation to the nearvision segment of the lens allows for a wearer of the lens to glanceupward or side to side and have near vision capability.

Another advantage of the bifocal contact lens of the present inventionis that the inherent "bottom heaviness" caused by cutting the distancevision segment on the upper portion of the lens, in addition to othernear vision benefits, decreases the mass from the upper portion of thelens. Thus, the lens is "bottom heavy" without adding unwanted prism.

In addition, it will be noted that other modifications may be madewithout departing from the present invention. For example, the bottomportion of the lens may be cut off or truncated to aid in lid engagingaction for lens translation.

The description of the preferred embodiments of the present inventionhas been presented for purposes of illustration and description, but isnot intended to be exhaustive or limit the invention in the precise formdisclosed. Many modifications and variations will be apparent topractitioners skilled in the art. The embodiment was chosen anddescribed in order to best explain the principles of the invention andthe practical application to enable others skilled in the art tounderstand the invention for various embodiments and with variousmodifications as are suited for the particular use contemplated.

What is claimed is:
 1. A single component bifocal contact lens having aposterior surface formed to fit a human cornea, an anterior surface, anupper portion and a lower portion when viewed in a planar view, saidsingle component bifocal contact lens comprising:a substantiallysemicircular distance vision surface disposed within said upper portionof said bifocal contact lens; a first near vision surface disposedwithin said lower portion of said bifocal contact lens; and a secondnear vision surface disposed within said upper portion of said bifocalcontact lens surrounding said substantially semicircular distance visionsurface.
 2. The single component bifocal lens of claim 1, wherein saidfirst near vision surface meets said distance vision surface at anoffset along a segment having opposing ends, said segment extendinghorizontally across said anterior surface, and said offset forming ashelf surface extending along said segment and extending perpendicularlyto at least one surface, wherein said shelf surface faces an upper lidof a wearer in actual use.
 3. The single component bifocal contact lensof claim 2, wherein said shelf surface decreases in width as said shelfsurface approaches said opposing ends.
 4. The single component bifocalcontact lens of claim 3, wherein said first near vision surface meetssaid distance vision surface at tangent proximate said opposing ends. 5.The single component bifocal contact lens of claim 1, wherein saidsingle component bifocal contact lens includes an optical axis, saiddistance vision surface includes a first radius of curvature and saidfirst near vision surface and said second near vision surface includes asecond radius of curvature, said first radius of curvature of saiddistance vision surface and said second radius of curvature of saidfirst near vision surface and said second near vision surface lie onsaid optical axis of said single component bifocal contact lens.
 6. Thesingle component bifocal contact lens of claim 1, wherein said singlecomponent bifocal contact lens is a soft bifocal contact lens.
 7. Thesingle component bifocal contact lens of claim 1 wherein said singlecomponent bifocal contact lens includes a radial edge and said upperportion contains a lenticular section formed along said radial edge ofsaid upper portion.
 8. A single component, single axis alternatingvision bifocal contact lens having an anterior surface and a posteriorsurface and having an upper section and a lower section, when viewed ina planar view, said single component, single axis alternating visionbifocal contact lens comprising:said posterior surface having a concaveshape adapted to fit a human cornea; said anterior surface subdividedinto a near vision segment and a distance vision segment, said nearvision segment having a near vision surface with a first radius ofcurvature, said distance vision segment having a distance vision surfacewith a second radius of curvature, wherein said first radius ofcurvature being smaller than said second radius of curvature; saiddistance vision segment being in a generally semicircular shape locatedin said upper section of said single axis alternating vision bifocalcontact lens generally centrally; said near vision segment located insaid lower section and extending into said upper section surroundingsaid distance vision segment; and said distance vision segment and saidnear vision segment meeting at an offset along segment with opposingends on a meridian dividing said upper section and said lower section,wherein said offset is greatest near a midpoint of said segment and saidoffset decreases towards said opposing ends, said offset forming a shelfsurface extending along said segment and extending from said near visionsurface to said distance vision surface along said segment, wherein saidshelf surface faces an upper lid of a wearer in actual use.
 9. A singlecomponent bifocal contact lens having an anterior surface and aposterior surface and having an upper portion and a lower portion whenviewed in a planar view, said single component bifocal contact lenscomprising:said posterior surface having a concave shape adapted to fita human cornea; said anterior surface subdivided into a near visionsurface and a distance vision surface, said near vision surface having afirst radius of curvature, said distance vision surface having a secondradius of curvature, wherein said first radius of curvature beingsmaller than said second radius of curvature; said distance visionsurface comprises a first zone surface located centrally in said upperportion of said bifocal contact lens, said first surface zone surfacebeing semicircular in shape; said near vision surface comprises a secondzone located in said lower portion of said bifocal contact lens and athird zone located in said upper portion of said bifocal contact lens,said second zone surface forming an annular semicircular segment aroundsaid first zone surface tangentially and meeting said second zonesurface along two segments lying along a meridian between said upperportion and said lower potion; and said first zone surface and saidsecond zone surface meeting along said meridian between said twosegments at an offset to form a shelf surface extending along saidmeridian between said two segments and extending perpendicularly to atleast one of said first and second zone surfaces, wherein said shelfsurface faces an upper lid of a wearer in actual use.
 10. The singlecomponent bifocal contact lens of claim 9, wherein said shelf surfaceformed by said offset between said first zone surface and second zonesurface decreases in width as said shelf surface approaches said twosegments.